Dopamine-sensitive receptors that evoke rumination and modify reticulo-ruminal activity in sheep

Dopamine (20 micrograms/kg) evoked rumination in sheep when injected as a bolus into the coeliac artery or into the left gastric artery but not when injected into the carotid artery. A mixed alpha-adrenoreceptor antagonist (phentolamine) and an alpha 2-adrenoreceptor antagonist (yohimbine) prevented dopamine from evoking rumination, but a dopaminergic antagonist (metoclopramide) did not. These findings suggest that dopamine stimulated rumination by acting upon alpha 2-adrenoreceptors situated in the area supplied by the left gastric artery, whereas dopamine injected intracerebrally may have evoked rumination by an alpha 2-adrenoreceptor effect in the central nervous system (Bueno et al., 1983) and the actions of intrajugular dopamine were exclusively upon peripheral adrenoreceptors located specifically in the gastric area. Dopamine (1 microgram/kg/min) infused into the carotid artery reduced the frequency of reticular contractions by acting upon a centrally located dopaminergic receptor mechanism sensitive to metoclopramide but not to phentolamine. When dopamine was infused into the coeliac artery or into the left gastric artery, the amplitude of reticular contractions was reduced by a peripheral mechanism sensitive both to metoclopramide and to phentolamine. Dopamine also reduced the amplitude of reticular contractions when infused into the carotid artery but to a lesser degree than when given into the coeliac or left gastric artery.     

Clinical field study to evaluate the efficacy and safety of the amino-acetonitrile derivative, monepantel, compared with registered anthelmintics against gastrointestinal nematodes of sheep in Australia

Objective   To determine the efficacy of monepantel, a developmental compound from the amino-acetonitrile derivative class of anthelmintics, against field infections of gastrointestinal nematodes in sheep.
Procedures   Comparisons of efficacy (using standard faecal worm egg count reduction tests) and safety (on the basis of visual observations) were made in a large-scale field study in Australia, between groups of sheep treated with either an oral solution of monepantel or a registered anthelmintic. The sheep were naturally infected with the major gastrointestinal nematode genera present in Australia.
Results   The post-treatment efficacy results for monepantel were: at 7 days (±1 day) efficacy was >98%; at 14 days (±1 day) it was generally close to or >99%; and at 21 days (±1 day) efficacy was consistently >99%. A high proportion of the targeted nematode populations were confirmed as being resistant to one or more of the currently available anthelmintic classes.
Conclusions   Monepantel when used under field conditions at a minimum dose rate of 2.5 mg/kg was highly effective against mixed-genus natural field infections of the major gastrointestinal nematode genera including Haemonchus , Teladorsagia ( Ostertagia ), Trichostrongylus , Nematodirus , Chabertia and Oesophagostomum . This result included efficacy against some populations resistant to the currently available broad-spectrum anthelmintics. Few Cooperia spp. were present to allow confirmation of efficacy against this genus. On no occasion after treatment did any commercial anthelmintic-treated groups have significantly lower faecal egg counts than the monepantel-treated groups. Monepantel was safe for the target animals and human operators when used in a field situation.     

Integrating practical, regulatory and ethical strategies for enhancing farm animal welfare

OBJECTIVE: To provide an integrated view of relationships between assessment of animal welfare. societal expectations regarding animal welfare standards, the need for regulation, and two ethical strategies for promoting animal welfare, emphasising farm animals. APPROACH: Ideas in relevant papers and key insights were outlined and illustrated, where appropriate, by New Zealand experience with different facets of the welfare management of farm animals. CONCLUSIONS: An animal's welfare is good when its nutritional, environmental, health, behavioural and mental needs are met. Compromise may occur in one or more of these areas and is assessed by scientifically-informed best judgement using parameters validated by directed research and objective analysis in clinical and practical settings. There is a wide range of perceptions of what constitutes good and bad welfare in society, so that animal welfare standards cannot be left to individual preferences to determine. Rather, the promotion of animal welfare is seen as requiring central regulation, but managed in a way that allows for adjustments based on new scientific knowledge of animals' needs and changing societal perceptions of what is acceptable and unacceptable treatment of animals. Concepts of 'minimal welfare', representing the threshold of cruelty, and 'acceptable welfare', representing higher, more acceptable standards than those that merely avoid cruelty, are outlined. They are relevant to economic analyses, which deal with determinants of animal welfare standards based on financial costs and the desire of the public to feel broadly comfortable about the treatment of the animals that are used to serve their needs. Ethical strategies for promoting animal welfare can be divided broadly into the 'gold standard' approach and the 'incremental improvement' approach. The first defines the ideal that is to be required in a particular situation and will accept nothing less than that ideal, whereas the second aims to improve welfare in a step-wise fashion by setting a series of achievable goals, seeing each small advance as worthwhile progress towards the same ideal. 'Incremental improvement' is preferred. This also has application in veterinary practice where the professional commitment to maintain good welfare standards may at times conflict with financial constraints experienced by clients.